[COLO-Frame,v16,29/35] COLO: Separate the process of saving/loading ram and device state

diff --git a/migration/colo.c b/migration/colo.c
index 61a5d16..8c05cdb 100644
--- a/migration/colo.c
+++ b/migration/colo.c
@@ -289,21 +289,37 @@  static int colo_do_checkpoint_transaction(MigrationState *s,
         goto out;
     }
 
+    colo_send_message(s->to_dst_file, COLO_MESSAGE_VMSTATE_SEND, &local_err);
+    if (local_err) {
+        goto out;
+    }
+
     /* Disable block migration */
     s->params.blk = 0;
     s->params.shared = 0;
-    qemu_savevm_state_header(trans);
-    qemu_savevm_state_begin(trans, &s->params);
+    qemu_savevm_state_begin(s->to_dst_file, &s->params);
+    ret = qemu_file_get_error(s->to_dst_file);
+    if (ret < 0) {
+        error_report("Save vm state begin error");
+        goto out;
+    }
+
     qemu_mutex_lock_iothread();
-    qemu_savevm_state_complete_precopy(trans, false);
+    /*
+    * Only save VM's live state, which not including device state.
+    * TODO: We may need a timeout mechanism to prevent COLO process
+    * to be blocked here.
+    */
+    qemu_savevm_live_state(s->to_dst_file);
+    /* Note: device state is saved into buffer */
+    ret = qemu_save_device_state(trans);
     qemu_mutex_unlock_iothread();
-
-    qemu_fflush(trans);
-
-    colo_send_message(s->to_dst_file, COLO_MESSAGE_VMSTATE_SEND, &local_err);
-    if (local_err) {
+    if (ret < 0) {
+        error_report("Save device state error");
         goto out;
     }
+    qemu_fflush(trans);
+
     /* we send the total size of the vmstate first */
     size = qsb_get_length(buffer);
     colo_send_message_value(s->to_dst_file, COLO_MESSAGE_VMSTATE_SIZE,
@@ -575,6 +591,16 @@  void *colo_process_incoming_thread(void *opaque)
             goto out;
         }
 
+        ret = qemu_loadvm_state_begin(mis->from_src_file);
+        if (ret < 0) {
+            error_report("Load vm state begin error, ret=%d", ret);
+            goto out;
+        }
+        ret = qemu_loadvm_state_main(mis->from_src_file, mis);
+        if (ret < 0) {
+            error_report("Load VM's live state (ram) error");
+            goto out;
+        }
         /* read the VM state total size first */
         value = colo_receive_message_value(mis->from_src_file,
                                  COLO_MESSAGE_VMSTATE_SIZE, &local_err);
@@ -607,8 +633,10 @@  void *colo_process_incoming_thread(void *opaque)
         qemu_mutex_lock_iothread();
         qemu_system_reset(VMRESET_SILENT);
         vmstate_loading = true;
-        if (qemu_loadvm_state(fb) < 0) {
-            error_report("COLO: loadvm failed");
+        colo_flush_ram_cache();
+        ret = qemu_load_device_state(fb);
+        if (ret < 0) {
+            error_report("COLO: load device state failed");
             qemu_mutex_unlock_iothread();
             goto out;
         }
diff --git a/migration/ram.c b/migration/ram.c
index 1f399a8..6edc039 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -2466,7 +2466,6 @@  static int ram_load(QEMUFile *f, void *opaque, int version_id)
      * be atomic
      */
     bool postcopy_running = postcopy_state_get() >= POSTCOPY_INCOMING_LISTENING;
-    bool need_flush = false;
 
     seq_iter++;
 
@@ -2501,7 +2500,6 @@  static int ram_load(QEMUFile *f, void *opaque, int version_id)
             /* After going into COLO, we should load the Page into colo_cache */
             if (ram_cache_enable) {
                 host = colo_cache_from_block_offset(block, addr);
-                need_flush = true;
             } else {
                 host = host_from_ram_block_offset(block, addr);
             }
@@ -2595,9 +2593,6 @@  static int ram_load(QEMUFile *f, void *opaque, int version_id)
 
     rcu_read_unlock();
 
-    if (!ret  && ram_cache_enable && need_flush) {
-        colo_flush_ram_cache();
-    }
     DPRINTF("Completed load of VM with exit code %d seq iteration "
             "%" PRIu64 "\n", ret, seq_iter);
     return ret;
diff --git a/migration/savevm.c b/migration/savevm.c
index 26e95d2..4296eab 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -929,6 +929,10 @@  void qemu_savevm_state_begin(QEMUFile *f,
             break;
         }
     }
+    if (migration_in_colo_state()) {
+        qemu_put_byte(f, QEMU_VM_EOF);
+        qemu_fflush(f);
+    }
 }
 
 /*